Drive mechanism of an electric timepiece

ABSTRACT

In an electrical timepiece a pair of drive coils are formed in an elliptical configuration with the major axes thereof disposed substantially tangentially to the circumference of the drive wheel at diametrically opposed positions. The drive magnets each have a rectangular configuration and the major axis of each magnet is disposed parallel to a respective tangent to the circumference of the drive wheel. The impulse pin on the drive wheel which imparts movement to the star wheel is angularly offset relative to the center line between the drive wheel and the star wheel.

United States Patent Nikaido et al.

DRIVE MECHANISM OF AN ELECTRIC TIMEPIECE Inventors: Akira Nikaido, Tokyo; Mitsuo Onda, Oomiya; Takayasu Machida, lruma; Fumio Nakajima, Tokyo; Takashi Toida, Tokyo; Yoshihiko Yanagawa, Tokyo, all of Japan Citizen Watch Company Limited, Tokyo, Japan Filed: Jan. 11, 1972 Appl. No.: 216,968

Assignee:

Foreign Application Priority Data Feb. 1, 1971 Japan 46-3707 US. Cl. 58/28 A, 310/36 Int. Cl. G04c 3/04 Field of Search 58/23 D, 28 R, 28 A, 28 D;

References Cited UNITED STATES PATENTS Haag 58/28 A Biemiller et a1. 58/28 D May 7, 1974 3,601,974 8/1971 Haag 58/28 A 3,568,431 7/1969 Schaad 58/28 R 3,646,750 3/1972 Reich 58/28 A 3,555,810 1/1971 Meitinger 53/23 R FOREIGN PATENTS OR APPLICATIONS 1,178,795 9/1964 Germany 58/28 A Primary ExaminerRichard B. Wilkinson Assistant Examiner-Edith Simmons Jackmon Attorney, Agent, or FirmSughrue, Rothwell, Mion, Zinn & Macpeak [5 7] ABSTRACT In an electrical timepiece a pair of drive coils are formed in an elliptical configuration with the major axes thereof disposed substantially tangentially to the circumference of the drive wheel at diametrically opposed positions. The drive magnets each have a rectangular configuration and the major axis of each magnet is disposed parallel to a respective tangent to the circumference of the drive wheel. The impulse pin on the drive wheel which imparts movement to the star wheel is angularly offset relative to the center line between the drive wheel and the star wheel.

2 Claims, 7 Drawing Figures DRIVE MECHANISM OF AN ELECTRIC TIMEPIECE This invention relates to a drive mechanism of an electric timepiece wherein a mechanical vibrator is brought into and kept in oscillation by reception of a series of timebase synchronizing pulses delivered from a timebase signal generating source, for driving a gear train of the movement of said timepiece. It relates more specifically to the drive mechanism of the above kind which is adapted for use in a crystal oscillator type small timepiece, especially a wrist watch.

Generally speaking, the timepiece of the above kind is liable to receive disturbing shocks and similar mechanical adverse influences from outside, whereby the predetermined frequency of the mechanical vibrator fitted in the interior of the timepiece is subjected to disadvantageous fluctuations. As a result, the oscillative movement of the mechanical vibrator and the timebase synchronizing pulses will become out of phase to each other and the drive efficiency will drop correspondingly. Under extreme conditions, the stepping motion of the timepiece movement may come to a dead stop. In order to avoid these frequently encountered distrubances, crystal oscillator type watches should preferably have:

a substantial resistance to the out-of-phase relationship between the oscillation of mechanical vibrator and the fed synchronizing pulses, and

a small-size of the drive mechanism which is capable of operating with a low power consumption.

It is a main object of the invention to provide a drive mechanism of the kind above referred to and satisfying substantially the above requirements.

A further object is to provide an improved drive mechanism of the above kind which is highly stable in its operation even if it should be subjected to outside mechanical disturbances.

A still further object is to provide a drive mechanism above referred to which can utilize a mechanical vibrator having a high frequency of operation.

A further object is to provide an electric timepiece movement having a superior self-starting performance without causing a motion stoppage of the mechanical vibrator and which is capable of attaining rather quickly the state of stabilized oscillation.

These and further objects, features and advantages of the invention will become more apparent when reading the following detailed description of the invention with reference to the accompanying drawings illustrative of substantially a preferred embodiment of the invention in comparison with a conventional mechanism.

In the drawings:

FIG. 1 is a plan view of a crystal oscillator type electric watch fitted with the drive mechanism according to this invention.

FIG. 2 is a part of an enlarged section taken substan tially along a section line Il'-II' shown in FIG. 1.

FIG. 3 is a part of a sectional plan view taken substantially along a section line III-III shown in FIG. 2.

FIG. 4 is a similar view to FIG. 3, illustrating, however, a conventional comparative drive mechanism.

FIG. 4a is a partial view similar to FIG. 4.

FIG. 5 is a diagram showing the relationship between the phase of oscillation of the mechanical vibrator and the timepiece synchronizing pulses, in the case of a prior known drive mechanism.

FIG. 6 is a similar diagram embodying the novel principle of the invention.

Referring now to the accompanying drawings, especially FIGS. 1-3 thereof, numeral 1 represents a conventional pillar plate of a watch, upon which bridges 2 and 3 are rigidly mounted. A conventional crystal oscillator block 4, oscillator circuit block 5, condenser block 6, trimmer condenser block 7, lead plates 8 and 9 and battery block 10 are rigidly attached to the bridges. These blocks may be of the conventional design and are thus shown in substantially their outline configurations only. The crystal oscillator block 4 is shown in FIG. 1 in dotted line only, showing the position thereof relative to related parts. As will become more clear, these blocks and plates constitute in combination a conventional crystal oscillation circuit, a frequency dividing circuit and a drive circuit.

A drive coil unit 11 is rigidly attached to the bridge 3 by means of an adhesive.

Second drive coil unit 13 is attached fixedly to a coil supporting plate 12 which is rigidly mounted on the pillar plate 1 by screw means, not shown.

First drive coil 11 is connected electrically by lead means 103 to an amplifier circuit block 102, a frequency divider circuit block 101 and the oscillator circuit block in succession one after another, as schematically shown in FIG. 3, so as to receive timebase synchronizing pulses. Second drive coil unit 13 is designed and arranged in the similar way, as seen from the same figure. Although these coils 11 and 13 are connected electrically in parallel to each other, a series connection can be employed, if occasion may desire, and with equal results. As seen, each of these coil units 11; 13 is formed into nearly an elliptical shape having its longer axis positioned substantially parallel to tangents to drive discs 18; 19.

In FIG. 3, it should be noted that drive wheel 114 and coils ll, 13 are arranged relatively in such a way that the center 0 of said wheel and the centers 11b, 13b of coils 11 and 13 are positioned on an imaginary straight line 14a. Furthermore, the major axes 11a and 13a of the elliptical coils ll, 13 are arranged at right angles to said imaginary center-to-center line 14a. The major and minor axes of permanent magnet 37 are shown at 37a and 37b, respectively and are representative of all of the major and minor axes of each of the magnets. Arrow represents the width of the coil 13. As clearly seen from FIG. 3, the axial length or major axis 37a of the magnet 37 is selected to be larger than the width 12c of the related coil 13. This applies to each of other permanent magnets.

Numeral 14 denotes generally a drive wheel including said discs l8; l9 and having a general configuration similar to that of a conventional balance wheel. A vertically arranged drive arbor 15 rigidly carries these discs through supporting pieces l6; 17, respectively, which are rigidly attached to the arbor by press-fitting or similar conventional means.

Drive arbor 15 is provided rigidly with a disc 21 having an impulse pin 20 secured thereto as in the case of a conventional balance wheel. Adjacent its upper end, the arbor 15 is provided rigidly with a collet 23, one end of a hair spring 22 being fixedly attached to the latter conventionally.

The drive wheel 14 with its arbor 15 is rotatably mounted at its lower and upper ends in conventional antifriction bearings and 26 respectively, which are mounted in turn in the pillar plate 1 and a stationary support member or bridge 24 fixedly attached thereto, although the attaching means have been omitted from the drawing only for simplicity.

The support member 24 mounts rotatably a stud cock 27 carrying rigidly a stud 28 for fixedly attaching the outer end of hair spring 22, conventionally.

A regulator member 29 is rotatably mounted on the support member 24, and a regulator pin 30 is attached fixedly to said member 29. The hair spring 22 is supported by its one end by a stud pin 31. As conventionally, the natural oscillative frequency of the drive wheel 14 may be varied in response to occasional demands, by modifying the effective length of the hair spring 22, especially for bringing the oscillative frequency substantially into coincidence with the frequency of the reference synchronizing pulses. Numeral 32 represents a fine adjusting plate adapted for cooperation with an eccentric screw 33 provided for fine adjustment of the said regulator member 29.

Disc 18 carries fixedly four radially arranged permanent magnets 34-37. In the similar way, disc 19 carries fixedly four radially arranged permanent magnets 38-41. Each series of permanent magnets carried on discs 18 and 19 are positioned in alignment with each other as seen in FIG. 3. Each of these permanent magnets is shaped into substantially a rectangular form when seen in FIG. 3, having its longitudinal axis positioned in parallel to a related tangent although the latter has not been shown only for simplicity. As seen from FIG. 2, these permanent magnets are arranged with small idle gaps relative to the drive coils 11 and 13 which are arranged on an imaginary horizontal common plane. There are thus established two flux passages, one passing through permanent magnets 34;38, drive disc 19, permanent magnets 39,35, and drive disc 18 one after another, and the other passing through magnets 36;40, disc 19, magnets 4l;37 and disc 18 one after another. Thus, these flux passages are interlinking with said drive coils 11 and 13, thereby generating electromagnetic forces between the magnets and the drive coils. v v

As shown in FIG. 3, in the case where the major axes 11a, 13a are positioned at right angles relative to the imaginary line 14a and two pairs of the substantially rectangular permanent magnets 37(41), 34(38) are mounted fixedly on drive wheel discs 18, 19 in symmetry with magnets 36(40), (39), they are magnetically coupled with coils ll, 13, respectively. In this case, attention should be directed to the fact that all the surfaces of these magnets in opposition to the related coils are of the same magnetic polarity. For instance, those surfaces of magnets 34,36 in opposition to the related coils are all S," while the opposite surfaces of these magnets are all N.

In FIG. 3, the drive wheel 14 is shown in its stationary position wherein the impulse pin 20 is positioned at an angularly offset angle alpha relative to a center-tocenter line 0-0 connecting the center 0 of the drive shaft 15 with the center 0' of star wheel 42 and when measured in thereversed angular direction relative to the rotational direction B of the star wheel 42, thus being positioned remote from the peripheral teeth 42a of the wheel 42.

Star wheel 42 is made of a magnetic material and is rotatably mounted by and between pillar plate 1 and a gear train-supporting plate 43 whichis fixedly attached thereto, as conventionally known although the fixing means have been omitted from the drawing only for simplicity.

Numeral 44 denotes a positioning magnet comprised by a kind of a permanent magnet positioned fixedly on pillar plate 1 and in close proximity to the peripheral teeth 42a of star wheel 42 thereby influencing by its magnetic attracting force upon the wheel 42 the correct positioning of the latter.

A pinion 45 is concentrically attached fixedly to said star wheel 42 and kept in meshing with a conventional fourth gear 47 to which a fourth pinion 46 is fixedly and concentrically attached. Fourth pinion 46 is kept in meshing with a third gear 48 attached fixedly and coaxially with a third pinion 49. The third gear, third pinion, fourth gear and fourth pinion constitute members of the conventional time-keeping and display gear train.

In FIG. 4, there is shown a comparative conventional mechanism for comparison, in a highly simplified way.

In this representative prior art, drive disc '19 is rotatably mounted by and between the pillar plate, not shown, and a supporting bridge, now shown, and carries fixedly four drive magnets 38', 39', 40'and 41' which are positioned with the smallest possible idle gaps relative to drive coils 11' and 13' shaped into circular discs which are fixedly attached onto a mounting member, not shown. A disc 21 is fixedly mounted on said drive disc 19' and mounts fixedly in turn an impulse pin 20 which is kept in meshing with teeth 42a on a star wheel 42' rotatably mounted by and between pillar plate, now shown, and a gear-mounting bridge or similar member.

The star wheel 42' is made of magnetic material and subjected to the positioning influence of a positioning magnet 44' which is fixedly mounted on the pillar plate.

FIG. 4 shows the drive disc 19' held in'its stationary position. In this position, the impulse pin 20' is positioned substantially on the center-to-center line connecting the center 0 of the drive shaft and the center 0' of said star wheel. FIG. 4a shows disc 19' after movement.

FIG. 5 represents an operational wave chart of the conventional drive mechanism, while FIG. 6 shows a similar chart of the improved drive mechansim according to this invention.

In these charts, curve a represents the induced voltage at the terminals of said drive coils 11 and 13 when the drive wheel 14 is kept in its oscillating position and the drive coils 11 and 13 are electromagnetically interrelated. This curve shows, at the same time, the distribution of the number of interlinked fluxes between drive coils 11; 13 and the drive magnets.

Rectangular wave b represents the reference synchronizing pulses which are derived from the reference oscillation signal delivered from crystal oscillator 4 upon proper frequency division and wave shaping by means of conventional means, not shown. The period of the thus frequency-divided and shaped signal has a stabilized value of To. The drive wheel 14 has been previously designed to oscillate at a constant period substantially equal to said period T0 of the reference synchlonizing pulses. By application of these reference synchlonizing pulses to drive coils 11 and 13, the drive wheel 14 is brought into oscillation at the specified period T0, and the impulse pin mounted fixedly on drive wheel 14 will drive star wheel 42 intermittently in the direction B so that the time-keeping gear train is kept in its regular position.

Since the drive mechanism according to this invention comprises a pair of drive coils 11 and 13, having their respective longer axes extending across the disc 19 perpendicular to the center line between the coils 11 and 13 and the drive disc 19, and permanents magnets 34-41 having axes directing substantially in the parallel directions to respective tangents, the distribution (t1) of flux interlinkages between the drive coils and the permanent magnets can be set to a substantially larger value than that (t2) attainable with the conventional drive mechanism of the comparative nature, as may be easily seen from comparison of FIG. 6 with FIG. 5.

As a result, the drive mechanism according to this invention has a superior structure over the comparative conventional one and is highly resistant to outside disturbing causes.

When the oscillation of drive wheel 14 fluctuates under the influence of an outside disturbing cause, the wave form a will become a, as an example thereby the period being changed over to T. Therefore, there will be a substantial difference between T and To. With use of the conventional drive mechanism and with application of the reference synchronizing pulses, the synchronizing force can not practically develop, by virtue of almost nil value of the interlinked fluxes. Under extreme conditions, an out-of-phase oscillation could occur and this condition should become so severe that the application of the reference synchronizing pulses will act upon the drive wheel in the oscillation preventing sense. On the other hand in the case of the present invention as shown in FIG. 6 as an example, the interlinked flux distribution value (t1) can be selected to a larger value so that the synchronizing force can generate even when the oscillation of the drive wheel fluctuates to are period T, and the occasionally introduced phase difference may be effectively and rapidly reduced, so as to recover the original standardized oscillation conditions.

The drive mechanism according to this invention has a favorable starting characteristics.

In comparison therewith, the drive mechanism according to the prior art, when the reference synchronizing pulses are applied to the drive wheel when it is in its stationary position, drive disc 19 will starts gradually to oscillate and the impulse pin 20 will act upon the star wheel 42' to cause the latter to oscillate against the magnetic attracting and positioning force exerted by positioner magnet 44'. With increasing development of the oscillative movement, star wheel gear teeth 42a will escape from the binding effect by the positioner 44 and the wheel 42 will initiate its intermittent movement in the direction of the arrow B so that the timekeeping gear train will initiate its regular going.

In the case of a smaller timepiece, especially a crystal oscillator type watch, the developing speed of the oscillative movement of drive disc 19' is substantially slow and the collision between impulse pin 20' and star wheel teeth 42a will rather disturb the desired establishment of the regular oscillation. Under extreme cases, the oscillative movement of the star wheel is brought to a dead stop on account of such engagement of impulse pin 20 with the star wheel teeth 42a. According to the prior art, the impulse pin and the star wheel teeth must be finished to provide dimensions, so as to avoid otherwise possible operational disturbances of the above kind.

On the contrary, in the case of the present invention, the impulse pin 20 is positioned substantially in a spaced relationship relative to the star wheel teeth 42a with the drive wheel 14 in its stationary position and thus upon application of the reference synchronizing pulses, the drive wheel 14 will be brought more quickly into its oscillating movement and without engagement of the drive wheel 14 with the star wheel 42, thereby a highly favorable chance being provided to enhance substantially the development of the oscillating motion.

Upon development of the oscillation to a certain degree and with the star wheel teeth 42a having been escaped from the influence of the binding effect exerted by the positioner magnet 44, the wheel 42 will start to make intermittent rotation. In this respect, the aforementioned offset positioning of the impulse pin has a grave importance.

Finally, it should be noted that FIG. 2 represents a kind of developed sectional elevation wherein the relative position of the constituting gears are somewhat shifted so as to more clearly show the respective gearmesh conditions.

The embodiments of the invention in which an exclusive property or privilege is claimed are as follows:

1. An electro-mechanical motion converter for a timepiece comprising drive cells, a plurality of drive magnets and a drive wheel means carrying said drive magnets, said coils each being shaped in a substantially elliptical form with the centers of said coils and said drive wheel means being disposed in a straight line with the major axis of each being positioned perpendicular to said straight line across said drive wheel means and said drive magnets each being shaped into a substantially rectangular form with the major axis of each of said rectangles being arranged in a direction parallel to a related tangent to said drive wheel means whereby upon application of signals to said coils said drive magnets will be magnetically coupled with said coils.

2. An electro-mechanical motion converter for a timepiece as set forth in claim 1 further comprising an impulse pin mounted for rotation with said drive wheel means and a star wheel for driving a conventional timekeeping gear train in said timepiece, said impulse pin being positioned at an angularly offset position relative to the center-to-center line connecting the centers of said drive wheel and said star wheel when observed with both wheels in their stationary position. 

1. An electro-mechanical motion converter for a timepiece comprising drive cells, a plurality of drive magnets and a drive wheel means carrying said drive magnets, said coils each being shaped in a substantially elliptical form with the centers of said coils and said drive wheel means being disposed in a straight line with the major axis of each being positioned perpendicular to said straight line across said drive wheel means and said drive magnets each being shaped into a substantially rectangular form with the major axis of each of said rectangles being arranged in a direction parallel to a related tangent to said drive wheel means whereby upon application of signals to said coils said drive magnets will be magnetically coupled with said coils.
 2. An electro-mechanical motion converter for a timepiece as set forth in claim 1 further comprising an impulse pin mounted for rotation with said drive wheel means and a star wheel for driving a conventional timekeeping gear train in said timepiece, said impulse pin being positioned at an angularly offset position relative to the center-to-center line connecting the centers of said drive wheel and said star wheel when observed with both wheels in their stationary position. 